The invention is based on a priority application EP07300884.9 which is hereby incorporated by reference.
The invention relates to a method for scheduling of service data according to the preamble of claim 1, a user terminal according to the preamble of claim 11, a base station according to the preamble of claim 13 and a communication network according to the preamble of claim 14.
Typically, a base station in a cellular radio communication network comprises resource schedulers that allocate physical layer resources for the downlink and uplink transport channels used for communication with user terminals with different schedulers operating for the downlink and the uplink.
Scheduling of services like e.g. conversational and streaming services such as Voice over Internet Protocol (VoIP) in cellular radio communication networks is often performed taking into account the quality of service (QoS) requirements as well as the radio conditions in the corresponding serving radio cell, i.e. the scheduler preferably takes account of the traffic volume and the QoS requirements of each user terminal and associated radio bearers, when sharing resources like e.g. a frequency resource divided into resource blocks between user terminals.
Schedulers may assign physical layer resources taking into account the radio conditions at the user terminal identified through measurements made at the base station and/or reported by the user terminal.
Radio resource allocations can be valid for one or multiple so-called transmission time intervals (TTI).
Radio resource assignments comprise assignments of physical resource blocks (PRB) and modulation and coding schemes (MCS). Allocations for time periods longer than one transmission time interval might also require additional information, as e.g. allocation time or allocation repetition factor.
Basic scheduler operations are e.g. described in the document 3GPP TS 36.300 VL.0.0 (2007-03); 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2(Release 8) in the chapters 11.1 and 11.2.
One way of scheduling of radio resources with reduced signaling effort is to use persistent scheduling, i.e. scheduling with predefined transmission time intervals for the initial transmissions and retransmissions of transport blocks from a base station to a user terminal or with predefined transmission parameters, like e.g. the modulation and coding scheme (MCS). If retransmissions are performed synchronously, i.e. in a fixed timely relative offset to the initial transmission, the transmission time intervals for the retransmissions are predefined as well. As with such synchronous retransmissions all the transmission time intervals used for the transmission from the base station are predefined, there is no need for signaling to the user terminal the transmission time intervals that can be used by the base station for sending data to the user terminal, which reduces the signaling effort.
However, persistent scheduling has the disadvantage of a potential waste of radio resources, as in the base station, transmission time intervals are reserved for transmission and retransmission to the user terminal that are unused in case of periods of silence in which the persistently scheduled radio resources are unused.
If for a service, the predefined radio resources remain unused, such as during silence periods in VoIP services, without further measures, the radio resources cannot be reallocated to other user terminals, because the user terminal originally assigned to these radio resources will try to demodulate and decode the transmission and generate a feedback, which is negative in this case.